Serotonin receptor cDNA cloned from Lymnaea stagnalis

Area of Science:

• Neuroscience
• Molecular Biology
• Pharmacology

Background:

• Serotonin (5-HT) is a crucial neurotransmitter in molluscs, impacting behavior, neuronal plasticity, learning, and memory.
• While serotonin transmission is understood, the pharmacology and diversity of its receptor system in molluscs remain largely unexplored.

Purpose of the Study:

• To clone and characterize a novel serotonin receptor from the mollusc Lymnaea stagnalis.
• To investigate the molecular and pharmacological properties of this newly identified receptor.

Main Methods:

• Cloning of the 5HTlym receptor gene based on homology with G protein-coupled receptors.
• RNA blot-hybridization to detect mRNA species in the central nervous system.
• Transient expression in COS-7 cells for receptor binding assays using [3H]lysergic acid diethylamide.

Main Results:

• A putative G protein-coupled receptor, 509 amino acids long, was cloned and named 5HTlym.
• The 5HTlym receptor shows highest homology to Drosophila and mammalian 5HT1 receptors.
• Two mRNA species (2.3 and 3.2 kb) were detected in the Lymnaea central nervous system.
• Transient expression revealed saturable radioligand binding with a dissociation constant of 0.9 nM.
• The 5HTlym receptor exhibits unique pharmacology, not fitting mammalian classifications but sharing traits with mammalian vascular 5HT1-like receptors.

Conclusions:

• The cloning and characterization of the 5HTlym receptor provide new insights into the diversity of serotonin receptors in invertebrates.
• This receptor's unique pharmacological profile highlights potential differences in serotonin signaling pathways between molluscs and mammals.
• The findings contribute to understanding the molecular basis of serotonin's role in molluscan neurobiology.